Testing loops in context of different stem-sequences.

<p>The shRNA cassettes were either introduced stably using retroviral vector (<b>A</b>) or transiently from a plasmid co-transfections with a firefly luciferase reporter construct containing the eGFP target sequence (<b>B</b>). eGFP levels were measured by Flow cytometry. Asterisk denotes the control shRNA containing the loop previously published by Brummelkamp et al. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0043095#pone.0043095-Brummelkamp1" target="_blank">[11]</a>.